apex: choose stub according to min_sdk_version

Native modules within APEX should be linked with proper stub version
according to its min_sdk_version.

For example, when min_sdk_version is set to "29", libfoo in the apex
would be linked to libbar of version 29 from platform, even if it has
a newer version like 30.

Bug: 145796956
Test: m nothing (soong tests)
Change-Id: I4a0b2002587bc24b7deeb5d59b6eeba5e1db5b1f
diff --git a/cc/linkable.go b/cc/linkable.go
index e4f034c..80cd6b8 100644
--- a/cc/linkable.go
+++ b/cc/linkable.go
@@ -26,6 +26,7 @@
 	BuildStubs() bool
 	SetBuildStubs()
 	SetStubsVersions(string)
+	StubsVersion() string
 	HasStubsVariants() bool
 	SelectedStl() string
 	ApiLevel() string